Aircraft and conveyor belt (again)
- Thread starter Observer
- Start date
Sponsored Links
Megawatt,
I am a flight engineer, with nearly 8,000 hrs in my log book.
Back to the discussion, rather than focussing on personal attacks.
Of course, thrust is at the heart of the question. Whatever the amount of thrust, the aircraft will accelerate to the point that drag equals thrust and constant speed is then achieved. The wheels will free-wheel and they do not enter the discussion in aerodynamics.
However, unfortunately, the question places a condition that the speed of the wheels (it doesn't matter what speed it is) is exactly matched by the belt in the opposite direction. This means that the wheels cannot make any progress along the surface of the belt. Therefore, the aircraft cannot move relative to the belt, but the thrust theory says it must. I say again, the question is based on false conditions.
You mentioned a small model on a supermarket belt which you push forwards with your finger. Obviously, the model will move forward but, to do so, its wheels must rotate faster than the belt to enable it move forward on the belt while in contact with it, which goes against the condition of the question.
However, if the belt was also free-wheeling, the aircraft would take off because the aircraft's wheels would spin faster than the belt, due to thrust, and it would progress along the belt until it reached Vr.
I am a flight engineer, with nearly 8,000 hrs in my log book.
Back to the discussion, rather than focussing on personal attacks.
Of course, thrust is at the heart of the question. Whatever the amount of thrust, the aircraft will accelerate to the point that drag equals thrust and constant speed is then achieved. The wheels will free-wheel and they do not enter the discussion in aerodynamics.
However, unfortunately, the question places a condition that the speed of the wheels (it doesn't matter what speed it is) is exactly matched by the belt in the opposite direction. This means that the wheels cannot make any progress along the surface of the belt. Therefore, the aircraft cannot move relative to the belt, but the thrust theory says it must. I say again, the question is based on false conditions.
You mentioned a small model on a supermarket belt which you push forwards with your finger. Obviously, the model will move forward but, to do so, its wheels must rotate faster than the belt to enable it move forward on the belt while in contact with it, which goes against the condition of the question.
However, if the belt was also free-wheeling, the aircraft would take off because the aircraft's wheels would spin faster than the belt, due to thrust, and it would progress along the belt until it reached Vr.
Sponsored Links
Based on your misunderstanding of this problem, that claim scares me.kevnurse said:
No (sigh), it means that the wheels rotate, and that they will rotate at twice the speed that they would if the belt (or ground) were static.
It must, and it does, unless you're a fan of the exploding wheels theory.
and the belt would move at that same speed because the question says it must. Its a condition of the question. That condition makes the whole question impossible, as a concept. I'm not answering the question. I'm discussing the validity of the question. Your answer only works if the wheels rotate faster than the belt's speed, but the question does not allow you to do that. Its a flawed question.
No - it makes one interpretation of the question lead to a different answer.kevnurse said:
We've already been there and done all that. In spades.
Since I've given two answers (one for each of two interpretations of the question), which one are you referring to?
FFS.
Okay, so let's clear one thing up for the benefit of those here who don't know what flight engineers actually do ... You're a dial watching supernumery trolley dolly with the Royal Air Force. We can, therefore, remove the word Engineer from your list of qualifications.
I, like many others on here, am an engineer with, as it happens in this case, a degree in Aeronautical engineering and over 12 years experience in aircraft maintenance in my first career. I have also been a pilot since 1983 with over 5000 hours in my log book as pilot in command.
Now we've established our relative backgrounds ... Back to the discussion, rather than focusing on personal attacks ... Though I'm not excluding the need for further attacks if you keep posting stupid comments.
Not exactly ... The aircraft engines will accelerate until the point at which the thrust they produce overcomes the mass of the aircraft at which point it will begin to move and will continue to accelerate whilst thrust is in excess of aerodynamic drag and mass. Once takeoff velocity is reached the aircraft will lift off.
YES
This is the only thing you've posted which is 100% accurate and, if you can see this, I'm not sure how you then go on to post this ...This is where you really lose focus. It is totally irrelevant how the aircraft moves relative to the belt it is how the aircraft moves relative to the air that is the key factor i.e. how it moves relative to the ground either side of the belt and, as you have already said (quite correctly) the wheels freewheel and play no part in the take-off process other than the fact that they will be spinning a lot faster than normal ... And they stop the aircraft falling flat on its belly of course (for the pedants
)I do hope you manage to grasp this now, if not, why don't you go and ask one of your pilot chums or, better still, a qualified groundcrew engineer to educate you ... It'll give them a laugh if nothing else.
MW
Did you really mean to say that?
I am an ex plumbing engineer, with 1 O level (english language)
I, like many others on here, am an engineer with, as it happens in this case, a degree in Aeronautical engineering and over 12 years experience in aircraft maintenance in my first career. I have also been a pilot since 1983 with over 5000 hours in my log book as pilot in command.
... The aircraft engines will accelerate until the point at which the thrust they produce overcomes the mass of the aircraft at which point it will begin to move and will continue to accelerate whilst thrust is in excess of aerodynamic drag and mass. Once takeoff velocity is reached the aircraft will lift off.
YES
[ It is totally irrelevant how the aircraft moves relative to the belt it is how the aircraft moves relative to the air that is the key factor i.e. how it moves relative to the ground either side of the belt and, as you have already said (quite correctly) the wheels freewheel and play no part in the take-off process other than the fact that they will be spinning a lot faster than normal ... And they stop the aircraft falling flat on its belly of course (for the pedants
I do hope you manage to grasp this now, if not, why don't you go and ask one of your pilot chums or, better still, a qualified groundcrew engineer to educate you ... It'll give them a laugh if nothing else.
MW
and I concluded this at about page 2 of the LAST debate . How about posting a Q. about a Seaplane on an endless pool - Joined
- 14 Nov 2006
- Messages
- 119
- Reaction score
- 3
- Country
...Yawn
I see a familiar pattern developing. Lets not get the thread locked again.
If the Aircraft does not move forward, then the wheels do not spin, and the conveyor belt will not move.
Therefore the Aircraft must MOVE FORWARD for the conveyor to react.
The conveyor is reacting to the speed of the wheels, not the Aircraft.
The question is defective and posits an impossible situation.
The rig can only exist if the aircraft, the wheels and the belt are all stationary.
For any aircraft speed greater than zero, the belt speed is infinite.
If you disagree, read the original question and tell me what you think the belt and wheel speeds are, with an aircraft moving relative to a fixed point at a speed of 1mph.
The rig can only exist if the aircraft, the wheels and the belt are all stationary.
For any aircraft speed greater than zero, the belt speed is infinite.
If you disagree, read the original question and tell me what you think the belt and wheel speeds are, with an aircraft moving relative to a fixed point at a speed of 1mph.
Sponsored Links
